hey there if you havent fixed it yet:
i have the decompresion bug aswell, it happens after an update usually.
what you need to do is find the filename where the decompression stucks.
C:\Users\xxxx\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalCache\Packages
or whatever your path is go check the file name in the folder. it should be a lonely compressed file with the ending *.PART. just delete and start the update again.
eg.: fs-base-genericairports-0.1.52.fspackage.part